do { break; } while (0);

I just came up with this C construc, using break to jump out of a block;

do {
  if (! seems_suitable(a,b)) break;
  c=check_even_harder(a,b,);
  if (! c) break;
    be_tricky();
  return;
  } while (0);

do_it_the_old_way(a,b);

I was adding a code block before an existing block whose purpose was to filter out certain conditions to handle especially, and trying to avoid lots of nested if/else blocks. Without this foul trick the code would read:

if (seems_suitable(a,b)) {
  c=check_even_harder(a,b,);
  if (c) {
    be_tricky();
    return;
  }
}

do_it_the_old_way(a,b);

it works for me anyway .